Akademik Veri Yönetim Sistemi
Wind Energy Science Conference, Hannover, Almanya, 25 - 28 Mayıs 2021, cilt.10, ss.119-120
Airborne wind energy has been intensely studied by the researchers, especially in the last decade
(Ahrens, Diehl and Schmehl, 2014). It stems from the crosswind flight concept that was originally
introduced by Loyd (1980). The improvements in the micro-computer and sensor technology, helped
designers use complex control algorithms and paved the path to the development of airborne wind
energy concept as an alternative to the conventional wind turbines. This new concept is
advantageous when compared to the classical wind turbines since it can be used in higher altitudes
that have a bigger wind energy potential. Moreover, due to not needing a concrete construction it is
an applicable concept in offshore as well. Although there are different types and various design
philosophies behind, using a flying object that is connected to the ground by a tether in this evolving
technology is common.
In this study, a winged airplane is used as an energy supplier. The mathematical model of the
airplane is constructed that is composed of aerodynamic, environmental, gravitational sections and
nonlinear equations of motion. (Önen, 2015) The mathematical model uses the aerodynamic control
surfaces such as ailerons, elevator and rudder. In constructing the aerodynamic model, variation of
the nondimensional force and moment coefficients according to varying angles of attack, sideslip
angle and control surface deflections are analyzed and obtained using an analysis software. The
maximum power that can be generated according to varying wind speed conditions is calculated. The
control problem of the crosswind flight is addressed in the paper which is fundamental to the control
architecture of airborne wind energy systems. There are two main approaches in controlling airborne
systems. First approach is based on online optimization of the power output of the system,
employing nonlinear model predictive control (NMPC) (Ilzhöfer, Houska and Diehl, 2007; Houska and
Diehl, 2010; Canale, Fagiano and Milanese, 2007; Canale, Fagiano and Milanese, 2008). In the second
method a trajectory tracking control methodology is preferred that separates the optimal trajectory
estimation and control problem from each other. The second methodology is used in this paper and
the trajectory tracking problem is formed as shown in Figure 1. The trajectory tracking controller is
producing the angle commands by using the difference between the actual position of the aircraft
and the desired trajectory and is mainly based on geometrical considerations. (Jehle, 2012, p.28) The
quaternion based nonlinear attitude controller is designed, producing steering commands by using
the difference between the angle command that is produced by the tracking controller and the actual
attitude of the aircraft. By expressing the current attitude and the desired attitude with quaternions,
the attitude control is realized by using the so called “to-go” quaternions. (Ariyibi and Tekinalp, p.6)
The optimal trajectory estimation that is necessary to produce the maximum amount of power is not
addressed in this study and left as a future work. The response of the controller is tested in a
simulation environment by using a pre-defined trajectory.